1. Field of the Invention
The present invention relates to a belt unit and an apparatus to which a belt unit is attached.
2. Description of the Related Art
A conventional electrophotographic printer Incorporates a transfer belt unit therein.
FIG. 18 illustrates one such conventional transfer belt unit incorporated in a conventional electrophotographic printer.
Referring to FIG. 18, a transfer belt unit (referred to as belt unit hereafter) 3 is placed in position by positioning the belt case 8 with respect to an electrophotographic printer (referred to as printer hereafter) 1. The belt unit 3 includes primarily a transfer belt 4, a drive roller 5, an idle roller 6, a transfer roller, not shown, and a cleaning blade, not shown. The transfer belt 4 is an endless loop and is entrained about the drive roller 5 and the idle roller 6. The transfer belt 4 has a width greater than a maximum width of paper that is accepted by the printer 1.
The drive roller 5 has a surface formed of a highly frictional material and rotates about a shaft, not shown. The shaft has a gear, not shown, which is in mesh engagement with a drive gear not shown, provided on the printer side, so that a drive force is transmitted through the gears. When the drive roller 5 is driven in rotation, the transfer belt 4 runs. The idle roller 6 maintains moderate tension in the transfer belt 4 so that the transfer belt 4 runs smoothly. The shafts of the drive roller 5 and idle roller 6 are supported on a belt frame not shown, assembled on the belt case 8.
If the belt unit 3 is a user-replaceable component of the printer, the belt case 8 is formed with grooves therein, not shown, which ride on guide rails 9 provided in the printer 1. When the belt unit 3 is taken out of the printer 1 for maintenance or attached to the printer 1 after maintenance, the side frame 2 pivotally mounted to the printer 1 is opened and then the belt unit 3 is drawn out of or pushed Into the printer 1. After the belt unit 3 has been completely inserted into the printer 1, the belt unit 3 is finally locked with connections of the belt case S fitting to their counter parts on the printer 1.
The belt unit 3 may be attached to and detached from the printer 1 from the front side of the printer 1.
The side frame 2 is first opened and then the belt unit 3 is attached to or detached from the front side or lateral side of the printer 1. Thus, the aforementioned conventional belt unit 3 suffers from the problem that the printer 1 requires a larger floor space than it actually takes up.
The belt case 8 is directly positioned relative to the printer 1, so that the transfer belt 4 is indirectly placed in position in the printer 1. If the belt unit 3 is skewed so that the drive roller 5 and idle roller 6 are not accurately positioned in the printer 1, then the drive roller 5 and idle roller 6 are no longer parallel to each other, causing the transfer belt 4 to become somewhat twisted. As a result, the transfer belt 4 vibrates while rotating.
The belt case 8 is positioned with respect to the printer 1, thereby positioning the gear attached on the shaft of the drive roller 5 relative to the drive gear on the printer side. This indirect positioning of the two gears may cause the gears to mesh with poor accuracy, resulting in non-uniformity of the running speed of the transfer belt 4.
The present Invention was made in view of the aforementioned drawbacks of the conventional apparatus.
A belt unit includes at least two rollers mounted on a frame; a belt entrained about the at least two rollers and driven to run with a medium placed thereon; and a carrying handle that generally extends in a direction substantially perpendicular to a direction in which the belt runs. The carrying handle is pivotally attached to the frame.
When the carrying handle is left free to pivot, the carrying handle pivots toward the belt unit, the frame has a stopper provided thereon, the stopper abuts a part of the carrying handle to prevent the carrying handle from pivoting any further when the carrying handle is left free to pivot.
The carrying handle may be secured to the belt unit at a position off the center of gravity of the belt unit.
The belt unit includes a drive roller and an idle roller about which a belt is entrained and runs when the drive roller rotates, and a first bearing fitted to a longitudinal end of a shaft about which the drive roller rotates.
The apparatus includes a bearing-receiving portion and a locking member. The bearing-receiving portion receives the first bearing when the belt unit Is attached to the apparatus. The locking meter engages the bearing to firmly hold the first bearing in position when the first bearing is received in the bearing-receiving portion.
The belt unit includes a first gear attached to a shaft of the drive roller. The apparatus includes a second gear that moves into meshing engagement with the first gear when the belt unit is attached to the apparatus. The first gear and the second gear are positioned so that a line passing through a first center of the first gear and a second center of the second gear makes an angle with a vertical line passing through the first center, the angle being larger than a pressure angle between the first gear arid the second gear.
The belt unit further includes a second bearing attached to a shaft of the idle roller. The apparatus further includes a frame formed with a groove that receives the second bearing when the belt unit is attached to the apparatus. The groove has a portion that extends in a direction substantially parallel to the direction in which the belt runs, and in which the first bearing is slidable.
The frame has an inclined surface that upwardly extends from the bearing-receiving portion. When the belt unit is attached to the apparatus, the inclined surface guides the first bearing into the bearing-receiving portion.
The belt unit further includes a guide projection formed on the frame on a side of the idle roller remote from the drive roller. The apparatus further includes a vertical groove formed therein that extends in a direction substantially perpendicular to the direction in which the belt runs. The vertical groove guides the guide projection when the belt unit is attached to the apparatus.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.